What is an Intrusion Detection and Prevention System in cybersecurity?

Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS) are cybersecurity tools used to monitor network traffic and system activity for signs of malicious behavior or policy violations.

An intrusion detection and prevention system is designed to detect and alert. It passively monitors traffic, identifies suspicious activity, logs the details, and notifies security administrators.

However, it does not take direct action to block or mitigate the threat. Its primary role is to provide visibility into potential security issues so that appropriate measures can be taken

An IPS, on the other hand, performs all the functions of an IDS but also takes automated action to prevent threats. This might include blocking traffic from a malicious IP address, terminating harmful sessions, or modifying firewall rules to stop an ongoing attack.

How does IDS work?

At a basic level, Intrusion Detection System and Intrusion Prevention Systems works in two ways:

  • It checks for known attack signatures like specific attack patterns or behaviors linked to malware or exploits.
  • It also flags anomalies, such as behavior that doesn’t fit your network’s usual pattern, which could point to a new or unknown threat.

When an IDS/IPS detects suspicious activity, it can take different actions depending on the type of attack detected. These actions may include logging the event in a security audit log, alerting administrators, blocking the offending IP address from accessing the network, and even resetting the connection if necessary.

But there’s more to it. A good IDS can:

  • Monitor the health and performance of critical systems, servers, firewalls, routers, and spot early indicators of compromise.
  • Help IT teams sift through logs and audit trails that would otherwise take hours to analyze manually.
  • Make threat detection more accessible, thanks to interfaces that let even non-security teams view alerts and understand what’s happening.
  • Tap into a large threat signature database, helping detect well-known attacks quickly.
  • Notify the right people (your SOC team or IT staff) when something goes wrong, such as a breach attempt, suspicious user behavior, or a rogue connection.
  • In some cases, it even takes initial action like blocking a suspicious IP or isolating a system to minimize damage before a human can respond.

IDS vs. IPS: What is the difference?

IDS are monitoring solutions designed to search for signs of network intrusion. If the IDS system discovers an intrusion, it notifies information security professionals. IPS includes functionality for taking action on the discovered threat by blocking or remediating it.

The main difference between IDS and IPS is that IPS allows you to automate responding to detected threats, while IDS requires you to address attacks manually.

Feature Intrusion Detection System  Intrusion Prevention System 
Core function Monitors network traffic and detects suspicious or malicious activity Detects and actively blocks or mitigates malicious traffic in real-time
Response type Passive: Alerts administrators for manual action Active: Takes automatic preventive measures (e.g., blocking IPs, resetting sessions)
Deployment position Usually out-of-band (traffic is copied for analysis) In-line (placed directly in the traffic flow to stop threats immediately)
Impact on traffic No effect on traffic performance or continuity Can affect traffic latency or availability during false positives
False positive Risk Low risk of service interruption, but needs human validation Higher risk of blocking legitimate traffic if not properly tuned
Use case suitability Ideal for monitoring critical systems where uptime is a top priority Ideal for environments where automated response is essential (e.g., edge defenses)
Typical users Security Operation Centers (SOC), forensic analysts Perimeter defense systems, automated security appliances
Remediation Manual investigation and action by IT/security teams Automated blocking, throttling, or modifying traffic
Complexity and tuning needs Easier to deploy, lower risk of disruption Requires fine-tuning and regular updates to prevent false positives
Best for Visibility and alerting on suspicious activity Stopping known threats instantly before they reach internal systems

 

Recommendation: IDS may seem inferior to an IPS system, but it may be a better solution for cases when process continuity is vital, such as critical infrastructure objects. IPS cybersecurity solutions are prone to giving false positives, which negatively influence system usage.

Why Intrusion Detection and Prevention Systems (IDS/IPS) are important

Intrusion detection and prevention systems provide a layer of security to networks by monitoring and analyzing traffic for malicious activity. They can detect known and unknown threats, allowing organizations to respond to potential attacks before they cause damage.

What are the Benefits of IDS/IPS?

Here are some of the main benefits you need to know:

1. Enhanced threat detection

IDS/IPS security solutions continuously monitor network traffic using deep packet inspection and behavior-based analytics. This allows them to detect known and potential threats early in the attack lifecycle, before they escalate into full-blown breaches.

For example, an IDS detects repeated failed logins from a foreign IP address. This helps security teams identify and halt a credential-stuffing attempt before data is compromised.

2. Automated threat response

IPS can automatically block malicious traffic, quarantine endpoints, reset suspicious sessions, or deny access based on threat intelligence rules.

This rapid response capability significantly reduces dwell time and limits potential damage from fast-moving new threats like ransomware or DDoS attacks.

3. Reduced attack surface

IPS filters out malicious traffic and prevents unauthorized access attempts. In reality, it reduces the number of exploitable entry points into your network. This proactive defense mechanism limits attackers’ paths, hardening your infrastructure.

Even if a vulnerability is discovered, IPS can help block exploit attempts until a patch is applied.

4. Supports compliance and regulatory requirements

Many regulations and industry standards mandate using IDS/IPS to protect sensitive data. These include:

  • PCI DSS (for cardholder data)
  • HIPAA (for healthcare sensitive information)
  • GDPR (for personal data of EU citizens)

Usually, IDS systems are part of Network Traffic Analysis (NTA) and Network Detection and Response (NDR) software.

5. Improved network visibility and intelligence

IDS/IPS systems offer deep visibility into the flow and nature of traffic across your network. They can highlight suspicious patterns, detect anomalies, and even uncover misconfigurations or shadow IT.

Through advanced telemetry collection and threat correlation, Group-IB’s ecosystem provides complete visibility into malicious behaviors across endpoints, networks, and cloud infrastructure.

Combining this with threat intelligence from over 900+ tracked threat actors gives you the context needed to prioritize and act fast.

6. Scalability and seamless integration

This is quite a no-brainer. Modern IDS/IPS solutions are designed to plug into your SIEM, generation firewalls, EDR, and more. Through cross-tool collaboration, they share data, automate responses, and strengthen your overall detection methods and response capabilities. They also integrate with:

5 Types of Intrusion Detection Systems

There are five main types of IDS, each with its strengths, quirks, and ideal use cases. Let’s examine them in more detail.

1. Network Intrusion Detection System

Network-based IDS is a system that monitors traffic across the entire network from a central point to detect suspicious activity in real time.

This is your go-to if you want a bird’s-eye view of everything moving through your network. An NIDS sits at a key point, usually near your firewall or router, and monitors traffic going in and out.

It’s great for spotting external threats in real time and doesn’t require agents on every machine. But the trade-off is that it can get overwhelmed with too much traffic. And if you don’t fine-tune the rules for what it should look at, you might miss things buried in the noise.

Good for: Real-time alerts, perimeter defense
Not great for: Pinpointing where exactly an attack is happening inside the network

2. Network Node  Intrusion Detection System

Network Node IDS is a variation of network IDS that monitors traffic at the individual node or server level, with agents installed locally on each device. This one works like NIDS but on a smaller scale. Instead of one big checkpoint, you install small sensors (agents) on each node or server you want to monitor. Each one keeps an eye on local traffic.

Because each agent handles less data, it runs faster and is easier on system resources. The catch is that you must install and manage a bunch of them, and they all need to report back to a central dashboard. So it’s more setup, but also more precision.

Good for: Faster analysis, lower resource usage
Not great for: Simple deployment, you’ll need to manage multiple agents

3. Host Intrusion Detection System

Host IDS is a system installed on individual devices (like servers or workstations) that monitors internal activity such as file changes, system logs, and local behavior.

HIDS is excellent at catching insider threats or spotting changes to critical files. However, one drawback is that it often picks things up after they happen. So, unless you’re monitoring it closely, you might find out a bit too late.

Good for: Deep visibility into specific devices, insider threat detection
Not great for: Real-time network-wide alerts

4. Protocol-Based Intrusion Detection System

Protocol-Based IDS monitors the application layer’s explicit network protocols (typically HTTP/HTTPS). It’s often placed right in front of a web server to check if anything strange is happening with users’ interactions with your site.

It’s not a full-blown IDS on its own, but it’s a handy add-on that can catch things others might miss, like odd behavior in making requests.

Good for: Securing web servers and app front-ends
Not great for: Broader security coverage

5. Application Protocol-Based  Intrusion Detection System

Application Protocol-Based IDS is a system that monitors the communication between applications and services. It focuses on application-layer traffic and behavior, usually within backend environments.

It’s usually deployed on server clusters where multiple applications interact. It won’t protect your whole network, but it’s a solid add-on for environments where internal app communication matters (microservices, APIs, internal databases).

Good for: Monitoring app-to-app traffic, adding depth to host-level defenses
Not great for: Catch-all intrusion detection

Intrusion Detection System Methods

Depending on the type of system you choose, there are different types of IDS and IPS methods. The way they identify threats can vary quite a bit. Let’s walk through the main techniques:

1. Signature-Based Detection

This is the most traditional approach. A signature-based IDS looks for specific patterns of known attacks. Basically, you’re dealing with a list of “most wanted” intruders. If traffic in your network matches something on that list, the system flags it.

The upside is that it’s fast, efficient, and accurate when the attack is known. The downside is that if it’s something new, like a zero-day attack that’s never been seen before, it’s probably going to miss it. That’s because the security technologies rely entirely on their database, which needs to be constantly updated to stay effective.

2. Anomaly-Based Detection

This one takes a different approach. Instead of matching patterns, it builds a profile of what “normal” activity looks like on your network and watches for anything outside that baseline.

Let’s say your team usually logs in between 9 a.m. and 6 p.m. If someone suddenly logs in at 3 a.m. from an unfamiliar location, that might raise a flag. It doesn’t mean it’s definitely a threat or a security incident, but it’s unusual and worth checking out.

The strength is that anomaly-based IDS can catch brand-new or stealthy cyberattacks that don’t match any known signature. The trade-off, however, is that they’re a bit sensitive. Changes in normal behavior (like someone working late or testing a new tool) can trigger false alarms.

3. Hybrid Detection

Some security systems combine signature-based and anomaly-based approaches to cover more ground. This hybrid method checks for known threats and looks for anything that seems off. It gives you a broader safety net, great for spotting both the obvious and the unexpected.

The only challenge is that you might see more alerts, which means more to sort through. But honestly, in security, catching too many things is a better problem than missing something important.

Build a stronger security stack with Group-IB

By now, it’s clear that there’s no universal blueprint for intrusion detection. Each type of IDS brings something different to the table; some excel at catching known threats, others are better at spotting unusual behavior. But no single method is foolproof on its own.

That’s why modern cybersecurity strategies lean heavily on layered detection, integrating multiple types of IDS to monitor different entry points, behaviors, and computer systems. This combined approach drastically shortens detection and response times by covering more ground with greater precision.

At Group-IB, we’ve designed our Unified Risk Platform to support this philosophy. It consolidates threat detection, intelligence, and incident response into a single, adaptive environment, giving security teams a clearer picture and faster control over various threats.

Ready to take your intrusion detection strategy to the next level?

Discover how Group-IB’s Unified Risk Platform can help you build a more resilient, intelligence-driven defense. Get started today